Encapsulated sputtering target

ABSTRACT

Embodiments of the invention provide encapsulated sputtering targets for physical vapor deposition. In one embodiment, an encapsulated target contains a target layer containing a first metal or an oxide of the first metal disposed over a backing plate, an adhesion interlayer disposed between the target layer and the backing plate, and an encapsulation layer containing a second metal or an oxide of the second metal disposed over the target layer and an annular sidewall of the backing plate. The target layer is encapsulated by the backing plate and the encapsulation layer and the first metal is different than the second metal. In some examples, the first metal is lanthanum or lithium and the target layer contains metallic lanthanum, lanthanum oxide, or metallic lithium. In other examples, the second metal is titanium or aluminum and the encapsulation layer contains metallic titanium, titanium oxide, metallic aluminum, or aluminum oxide.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. Ser. No. 12/263,013(APPM/013342), filed Oct. 31, 2008, which is herein incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention relate generally to sputtering targets usedin physical vapor deposition (PVD) processes, and more specifically, toencapsulated sputtering targets.

2. Description of the Related Art

Lanthanum materials, including metallic lanthanum and lanthanum oxide,are often used in the manufacturing of electronic and semiconductordevices. Lanthanum materials have gained popularity for use in metalgate applications. Often, the lanthanum materials, as well as othermaterials, are deposited from a sputtering target during a PVD process.

However, due to the extremely hydrophilic nature of these material, whenexposed to water and oxygen within the air, a reaction may be invokedwhich may result in the creation of undesired contaminants on thesurface of the target. Lanthanum may be exposed to the ambient airduring shipping and handling or by installing the targets within the PVDchamber. The reactive nature of the lanthanum with air createsbyproducts such as fine crystalline particles that causes particulatecontamination in the PVD chamber and therefore severely compromises thedeposited materials on the substrate.

Therefore, there is a need to provide a sputtering target free orsubstantially free of contamination when exposed to air.

SUMMARY OF THE INVENTION

Embodiments of the invention provide encapsulated sputtering targets andmethods for preparing such targets prior to a physical vapor deposition(PVD) process. In one embodiment, an encapsulated target for PVD isprovided which includes a target layer containing lanthanum disposed ona backing plate, and an encapsulation layer containing titanium disposedon or over the target layer.

In some embodiments, the target layer contains a lanthanum material,such as metallic lanthanum, lanthanum oxide, lanthanum alloys, orderivatives thereof. Examples are provided in which the lanthanummaterial is metallic lanthanum or lanthanum oxide. In some examples, anupper surface of the target layer has a mean surface roughness within arange from about 16 μm to about 32 μm. The encapsulation layer maycontain titanium, such as metallic titanium. The encapsulation layer maybe deposited over or onto the target material by a vapor depositiontechnique. In one example, the encapsulation layer may be sputtered ontothe target material during a PVD process. The encapsulation layer mayhave a thickness within a range from about 1,000 Å to about 2,000 Å.

In another embodiment, an encapsulated target is provided which includesa target layer containing lithium disposed on a backing plate and anencapsulation layer on or over the target layer. The target layercontains a lithium material, such as metallic lithium. The encapsulationlayer may contain titanium, such as metallic titanium. The encapsulationlayer may be deposited over or onto the target layer by a vapordeposition technique, such as PVD.

In another embodiment, a method for preparing an encapsulated targetprior to a PVD process is provided which includes positioning anencapsulated target within a PVD chamber and exposing the encapsulationlayer to a plasma while removing the encapsulation layer and revealingan upper surface of the target layer. The method further provides thatthe encapsulated target contains a target layer disposed on a backingplate and an encapsulation layer disposed on or over the target layer.In one example, the target layer contains a lanthanum material, such asmetallic lanthanum or lanthanum oxide. In another example, the targetlayer contains a lithium material, such as metallic lithium. In anotherexample, the encapsulation layer contains a titanium material, such asmetallic titanium.

In other embodiments, the method further provides monitoring changes inthe plasma impedance to determine the removal of the encapsulation layerfrom the target layer while loaded within the PVD chamber. The plasmamay be generated within the PVD chamber by a radio frequency source. Inone example, the encapsulation layer is removed during target burn-inprocess, just prior to performing a PVD process. Thereafter, materialfrom the target layer may be sputtered to a substrate within the samePVD chamber as the burn-in process.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the inventioncan be understood in detail, a more particular description of theinvention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIGS. 1A-1D depict an encapsulated target, as described in embodimentsherein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation.

DETAILED DESCRIPTION

FIGS. 1A-1D illustrate schematic drawings of an encapsulated target 100according to embodiments herein. The encapsulated target 100 has abacking plate 102, a target layer 104, and an encapsulation layer 107.The encapsulation layer 107 may be deposited over or on the target layer104 to prevent the target layer 104 from being exposed to water andoxygen within the air. In one embodiment, the target layer 104 isencapsulated or enclosed by the backing plate 102 and the encapsulationlayer 107. In one example, the encapsulation layer 107 contains atitanium material, such as metallic titanium or a titanium alloy.

The target layer 104 may be deposited over or on the backing plate 102.The target layer 104 contains material to be sputtered onto a substrateprocessed in the PVD chamber. In one embodiment, the target layer 104contains a lanthanum material, such as metallic lanthanum, lanthanumoxide, lanthanum alloys, derivatives thereof, or combinations thereof.In another embodiment, the target layer 104 contains a lithium material,such as metallic lithium. The target layer 104 may have a thicknesswithin a range from about 2 mm to about 20 mm, preferably, from about 3mm to about 12 mm, and more preferably, from about 4 mm to about 8 mm,for example, about 6 mm. In a specific example, the target layer 104containing a lanthanum material has a thickness of about 0.25 inches(about 6.35 mm). Alternatively, in one embodiment, an interlayer 105 mayoptionally be disposed between the backing plate 102 and the targetlayer 104 to increase adhesion therebetween. The interlayer 105 maycontain a metal, such as a metallic solder. In one example, theinterlayer 105 contains an indium solder.

The backing plate 102 includes a target support flange 114 that rest onor is otherwise secured to an insulator ring (not shown) disposed on atop portion of the housing within the PVD chamber. The encapsulatedtarget 100 may be used in various PVD chambers, such as a radiofrequency (RF) PVD chamber. The target support flange 114 includes anO-ring groove 116 which is used to receive an O-ring (not shown). TheO-ring positioned within the O-ring groove 116 provides a seal betweenthe target support flange 114 and the insulator ring. The backing plate102 typically contains or is made from a conductive material, such assteel, stainless steel, iron, nickel chromium, aluminum, copper, alloysthereof, derivatives thereof, or combinations thereof. In one example,the backing plate 102 contains copper or a copper alloy. The copperalloy may be a copper chromium alloy and contain about 99% of copper andabout 1% of chromium, by weight. Copper alloys useful for the backingplate 102 contain copper and chromium, nickel, iron, silicon, lead,alloys thereof, or mixtures thereof.

FIG. 1B depicts the encapsulated target 100 with a circular geometry.The size of the encapsulated target 100 may be adjusted according to thedifferent sizes of substrates to be deposited to within the PVD chamber.In one embodiment, the diameter of the substrate to be processed may bewithin a range from about 200 mm to about 450 mm, for example, about 300mm. In one example, the encapsulated target 100 is sputtered onto a 300mm substrate. The diameter of the corresponding backing plate 102 may bewithin a range from about 18 inches to about 22 inches, preferably, fromabout 19 inches to about 21 inches, for example, about 20 inches. Thediameter of the corresponding target layer 104 may be within a rangefrom about 16.5 inches to about 18.5 inches, preferably, from about 17inches to about 18 inches, for example, about 17.5 inches. Thecorresponding tapered annular edge 110 may have a length along thediameter and on each side of the encapsulated target 100, within a rangefrom about 1 inch to about 2 inches, preferably, from about 1.25 inchesto about 1.75 inches, for example, about 1.5 inches. The diameter of thecorresponding encapsulation layer 107 may be within a range from about16.5 inches to about 18.5 inches, preferably, from about 17 inches toabout 18 inches, for example, about 17.75 inches.

FIG. 1C depicts a cross sectional view of the encapsulated target 100.In one embodiment, the encapsulation layer 107 is deposited over or onan upper surface 124 of the target layer 104, the annular sidewall 120,and the backing plate 102. The target layer 104 is preferably diffusionbonded or otherwise firmly affixed onto the backing plate 102 at theinterface 105. Alternatively, both the backing plate 102 and the targetlayer 104 can be made in a one-piece construction and contain the samesputtering material.

The encapsulated target 100 contains a tapered annular edge 110.Preferably, the central sputtering surface 108 is substantially flat andis disposed in a PVD chamber substantially parallel to a substratesupport upper surface. The tapered annular edge 110 extends to anannular sidewall 120 on the backing plate 102. The tapered annular edge110 extends radially outwards towards the interface 105 between thetarget layer 104 and the backing plate 102. The tapered annular edge 110provides a smooth transition from the flat central sputtering surface108 to the annular sidewall 120 of the target layer 104 and promotesdeposition uniformity by reducing abrupt changes in the sputteringsurface.

FIG. 1D depicts a cross sectional view of the encapsulated target 100with the encapsulation layer 107 on top of the target layer 104. Toprotect the target layer 104 containing lanthanum or another materialfrom reacting with water or oxygen in the ambient air during shippingand handling or the installation of the backing plate 102 within a PVDchamber, the encapsulation layer 107 is deposited onto the upper surface124 of the target layer 104. The deposition area covered by theencapsulation layer 107 includes the target layer 104 and the taperedannular edge 110. The encapsulation layer 107 may be disposed onsurfaces of the backing plate 102. In one example, the encapsulationlayer 107 may be disposed within the O-ring groove 116 on the backingplate 102.

The mean surface roughness (Ra) of the upper surface 124 of the targetlayer 104 may be about 100 microinches (μin) (about 2.5 μm) or less,such as about 10 μin (about 0.25 μm) or less. In one example, the meansurface roughness may be within a range from about 16 μin (about 0.41μm) to about 32 μin (about 0.81 μm). The encapsulation layer 107 mayhave a thickness within a range from about 500 angstrom (Å) to about3,000 Å, preferably, from about 1,000 Å to about 2,000 Å. In anotherembodiment, the encapsulation layer 107 contains a titanium material,such as metallic titanium, a titanium alloy, or sputtered titanium. Theencapsulation layer 107 contains at least one layer, but may containmultiple layers of the same material or different materials. In oneexample, the encapsulation layer 107 contains titanium sputtered ontothe target layer 104.

In an alternative embodiment, the encapsulation layer 107 may containother materials depending on the compositional compatibility between thetarget layer 104 and the encapsulation layer 107. Alternative materialsthat may be used as or contained within the encapsulation layer 107include aluminum, aluminum oxide, titanium oxide, or derivativesthereof.

The encapsulation layer 107 may be removed after shipping andinstallation of the backing plate 102 is complete using a standardtarget burn-in. In one embodiment, the encapsulation layer 107 isremoved during an initial target burn-in process. In another embodiment,a radio frequency source or a large magnet source within a PVD chambermay be used to remove the encapsulation layer 107 before proceeding toprocess substrate deposition. In yet another embodiment, plasmaimpedance within the PVD chamber may be monitored to determine theremoval of the encapsulation layer 107 from the target layer 104.

By depositing an encapsulation layer on top of a target layer withreactive material, the target layer may be protected from reacting withexternal substances, therefore preventing the reactive material fromproducing unnecessary byproducts and contamination to the chamber.Although embodiments disclosed herein describe applications usinglanthanum materials and lithium materials as target layers, the basicscope of the invention is applicable to other materials contained withina target layer provided that the material used for the encapsulationlayer is chemically compatible.

While the foregoing is directed to embodiments of the invention, otherand further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. An encapsulated target for physical vapor deposition, comprising: a target layer consisting essentially of a first metal or an oxide of the first metal disposed over a backing plate; an adhesion interlayer disposed between the target layer and the backing plate; and an encapsulation layer consisting essentially of a second metal or an oxide of the second metal disposed over an upper surface of the target layer and an annular sidewall of the backing plate, wherein the target layer and the adhesion interlayer are encapsulated by the backing plate and the encapsulation layer and the first metal is different than the second metal.
 2. The encapsulated target of claim 1, wherein the first metal is lanthanum or lithium and the target layer consists essentially of metallic lanthanum, lanthanum oxide, or metallic lithium.
 3. The encapsulated target of claim 1, wherein the second metal is titanium or aluminum and the encapsulation layer comprises a material selected from the group consisting of metallic titanium, titanium alloy, titanium oxide, metallic aluminum, and aluminum oxide.
 4. The encapsulated target of claim 1, wherein the backing plate comprises copper or a copper alloy and the adhesion interlayer comprises indium.
 5. The encapsulated target of claim 1, wherein an upper surface of the target layer has a mean surface roughness of about 100 μin or less.
 6. The encapsulated target of claim 1, wherein the encapsulation layer comprises metallic titanium and has a thickness within a range from about 1,000 Å to about 2,000 Å.
 7. The encapsulated target of claim 1, wherein the target layer has a thickness within a range from about 2 mm to about 20 mm.
 8. The encapsulated target of claim 7, wherein the target layer has a thickness within a range from about 4 mm to about 8 mm.
 9. The encapsulated target of claim 1, further comprising a tapered annular edge of the target layer, wherein the tapered annular edge has a length along the diameter of the target layer within a range from about 1 inch to about 2 inches.
 10. An encapsulated target for physical vapor deposition, comprising: a target layer consisting essentially of a first metal or an oxide of the first metal disposed over a backing plate; and an encapsulation layer consisting essentially of a second metal or an oxide of the second metal disposed over an upper surface of the target layer and an annular sidewall of the backing plate, wherein the target layer is encapsulated by the backing plate and the encapsulation layer and the first metal is different than the second metal.
 11. The encapsulated target of claim 10, wherein the first metal is lanthanum or lithium.
 12. The encapsulated target of claim 11, wherein the first metal is lanthanum and the target layer consists essentially of metallic lanthanum or lanthanum oxide.
 13. The encapsulated target of claim 11, wherein the first metal is lithium and the target layer consists essentially of metallic lithium.
 14. The encapsulated target of claim 10, wherein the second metal is titanium or aluminum and the encapsulation layer comprises a material selected from the group consisting of metallic titanium, titanium alloy, titanium oxide, metallic aluminum, and aluminum oxide.
 15. The encapsulated target of claim 10, wherein the backing plate comprises copper or a copper alloy and the adhesion interlayer comprises indium.
 16. The encapsulated target of claim 10, wherein an upper surface of the target layer has a mean surface roughness of about 100 μin or less.
 17. The encapsulated target of claim 10, wherein the encapsulation layer comprises metallic titanium and has a thickness within a range from about 1,000 Å to about 2,000 Å.
 18. The encapsulated target of claim 10, wherein the target layer has a thickness within a range from about 2 mm to about 20 mm.
 19. The encapsulated target of claim 10, further comprising a tapered annular edge of the target layer, wherein the tapered annular edge has a length along the diameter of the target layer within a range from about 1 inch to about 2 inches.
 20. An encapsulated target for physical vapor deposition, comprising: a target layer consisting essentially of metallic lithium disposed over a backing plate; an adhesion interlayer disposed between the target layer and the backing plate; and an encapsulation layer comprising a metal or an oxide of the metal disposed over an upper surface of the target layer and an annular sidewall of the backing plate, wherein the target layer and the adhesion interlayer are encapsulated by the backing plate and the encapsulation layer and the metal is not lithium. 